Compression of fluorinated hydrocarbons



Patented June 22, 1937 PATENT' OFFICE COMPRESSION g FLUORINATED HYDRO-ARBON S Frederick Baxter Downing, Carneys Point, and Anthony FrancisBenning, Pennsgrove, N. 3., assignorsto E. I. du Pont de Nemours &Company, Wilmington, Del., a corporation of Delaware v I No Drawing.

cation during such compression.

Gaseous fiuorinated aliphatic hydrocarbons,

particularly the fluorochloro hydrocarbons, have recently found ratherwide use as refrigerants. Thesecompounds, while advantageous in manyrespects, have a definite disadvantage overthe 1o strongly polarrefrigerants such as sulfur dioxide and ammonia in that they aregenerally miscible in all proportions with hydrocarbon lubricating oils.This property is disadvantageous because in a refrigeration system wherethe reserve supply of lubricant is in contact with the refrigerantvapor, the oil will dissolve the refrigerant resulting, particularlyduring shutdowns, in all of the refrigerant collecting in the oilreserve chamber. When now the machine is started up, violent ebullitionof'the refrigerant from the oil carries the lubricant with it into otherparts of the system, leaving the compressor without sufilcient oil tooperate properly. This, of course, causes undue wear. Hence, under suchconditions of operation, some means must be provided for the return ofthe lubricant to the compressor. In the case of sulfur dioxide andammonia, the oil dissolves but a small quantity of refrigerant and thedifficulty described above is not encountered.

It is an object of the present invention to provide a method ofcompressing gaseous fluorinated aliphatic hydrocarbons under new andimproved lubricating conditions. A further ob- Ject is to provide amethod of compressing gaseous fluorinated aliphatic hydrocarbonrefrigerants in the ordinary type of refrigeration system wherein thereserve supply of lubricant is in contact with the refrigerant vapor,characterized by the use of a lubricating fluid which has goodlubricating properties and which does not tend to dissolve excessiveamounts of the fiuorinated aliphatic hydrocarbon. More specific objectsare to accomplish the foregoing objects with fluorochloro aliphatichydrocarbons, and more particularly difiuorodichloromethane. Otherobjects will appear hereinafter. I

These objects are accomplished by employing liquid organic esters of'phosphorus acids as lubricants. in systems for the compression offluorinated aliphatic hydrocarbons.

Application March as, 1935, Serial No. 13,174

I Eramplel Difluorodichloromethane was compressed in the type ofcompressor ordinarily employed in household refrigerators usingtechnical tricresyl phosphate as a lubricant. The proportions oftechnical tricresyl phosphate corresponded with the volume'proportionsof oil normally employed in the usual sulfur dioxide householdrefrigerator compressor. Excellent results were obtained. Thedifiuorodichloromethane was not miscible with the technical tricresylphosphate as in the case of oil, and although a study ofthe solubilityproperties 'of tricresyl phosphate, as given below, indicates that someof the fluorochloro hydrocarbon will be dissolved by the organicphosphate ester, nevertheless this solvent action did not interfere withthe operation of the compressor and highly satisfactory results wereobtained both before and after shut-downs. No undue wear on thecompressor parts was evident.

Good results were also obtained in the compression ofdifiuorodichloromethane in a largesize compressor.

Technical tricresyl phosphate is a mixture of the esters and mixedesters of the isomeric cresols. Methods of obtaining it are known in theart. One method, for example, is to react a technical mixture of theisomeric cresols with phosphorous oxychloride.

Some of the properties of this material which affect its use for thepurpose described above are given below:

Properties of technical tricresyl phosphate periinent to its use as alubricant for fluorz'nated hydrocarbons Saybalt viscosity at F. secondsSaybolt viscosity at 210 F do 39. 6 Viscosity index. -50

. Pour point degrees F -20 Pour point saturated with CF2C12 d0 -20 Flashpoint (open cup) do 475 Fire point do 620 Almen film strength lbs. persq. in 30, 000 Solubility in CFzClz (77 F.) per cent 12 SolubilityCFzClz in tricresyl phosphate (77 F.) per cent 45 Of the propertiesgiven above, the high Almen film strength and non-miscibility withfluorochloro hydrocarbons may be noted as being especially desirable.

Example II Instead of difluorodichloromethane, mono- Example I withcorrespondingly good results.

Example III Tetrafluorodichloroethane may be compressed as in Example Iwith good results.

Similarly, the invention may be applied to the treatment of othergaseous fluorinated aliphatic hydrocarbons, as described, for example,in, Midgley, Henne and McNary, Reissue Patent 'No- 19,265, dated August7, 1934.

Instead of technical tricresyl phosphate, other 1 liquid organic estersof phosphorus may be employed as, for example, any of the following:tri- (ortho-cresyl) phosphate; tri (meta cresyl) phosphate;tri-(para-cresyl) phosphate; phenyldi-(ortho-, meta-, or para-cresyl)phosphates;

' mixed isomeric di-cresyl-phenyl phosphates; di-

phate, dimyristyl phosphate, dibutyl phosphate and dicyclohexylphosphate. Similarliquid organic esters of phosphorus, thiophosphoric,.meta-phosphoric and pyrophosphoric acids and mixtures containingthem maybe used. In general, we prefer-to employ the neutral and acidic estersof the phosphorus acids;

The term lorol is used to describe a mixture ofv esters or mixed estersderived from a mixture of alcohols containing mostly lauryl alcohol butalso containing some decyl and myristyl alcohols. The term ocenol isapplied to a mixture-of primary aliphatic alcohols having 12 to 18carbon atoms and consisting mainly of oleyl alcohol.

Such a mixture usually has an iodine value of,

about 50.

A preferred class ofthe organic phosphorus esters may be represented bythe following general formula:

where X, Y and Z represent H or lower aliphatic hydrocarbon radicalssuch as methyl, ethyl, isopropyl and butyl but maynot all be --H at thesame time, and m, n, and o are 1, 2 or 3. u

Another preferred class oforganic phosphorus esters for our purpose arethe normally liquid long chain aliphatic hydrocarbon monoand diesters ofphosphorus acids preferably having at least one carbon chain of eight ormore carbon atoms, e. g., dioctyl phosphate, monoand dilorol phosphates,monoand diocenol phosphates, and 4 octyl-lauryl phosphate.

A third preferred class of compounds are the normally liquid mixedaliphatic-aromatic difluorotrichloromethane may be compressed as inesters of phosphorus acids, as, for example, mixed tertiary amyl-phenylphosphate and lorol-cresyl phosphate.

The liquid organic esters of phosphorus acids are preferably employed inundiluted state, that is, without the-addition of material amounts ofsolvents or diluents, particularly those diluents which arepoorer'lubricants or tend to dissolve the fluorinated aliphatichydrocarbon. dilution is to be made non-polar lubricants rather thanpolar lubricants are preferred. Thus, polar lubricants typified bypolyhydric alcohols such as glycerin are not as good lubricants as theorganic phosphorus esterstypified by tricresyl phosphate.

This invention has been instrumental in solving one of the morediflicult problems in the compression of fluorinated hydrocarbons,particularly in the field of household refrigeration. It has also beensatisfactorily used in larger scale compression systems. i

As many apparently widely different embodiments of this invention-may bemade without dc parting from the spirit andscopethereof, it is" to beunderstoodthat we do'not limit ourselves to the'specific embodimentsthereof except as defined inthe appended claims. i

We claim: v 1

1. The method'of' compressing gaseous fluorinated aliphatic hydrocarbonswhich comprises compressing the gaseous fiuorinated hydrocarbons in thepresence of lubricants consisting of liquid organic esters of phosphorusacids, said If any liquid organic esters being substantially immisciblewith the fluorinated aliphatic hydrocarbons. 2. The method ofcompressing gaseous diflu-' orodichloromethane which comprisescompressing the difiuorodichloromethane in the presence'of a lubricantconsisting. of liquid organic esters of phosphorus acids having thefollowing general formula I where X, Y and Z represent -H or loweraliphatic hydrocarbonradicals but may'not all be H at the same time, andm, n, and '0 are 1, 2-or 3.

3. The method of compressing gaseous difluorodichloromethane whichcomprises compressing the difluorodichloromethane in. the presence of alubricant consisting of technical tricresyl .phosphate.

in: the gaseous fluorinated hydrocarbons in the presence of liquidorganic esters selected from the class consisting of aromatic diandtriesters of phosphorus acids, normally liquid long chain aliphatichydrocarbon monoand di-esters of phosphorus acids, and normally liquidmixed aliphatic-aromatic esters of phosphorus acids.

7. In the process of refrigeration which comprises condensing a gaseousfluorinated hydrocarbon refrigerant and then evaporating the same, thestep which comprises compressing said refrigerant in the presence ofliquid organic esters of phosphorus acids which are substantiallyimmiscible in said refrigerant.

8. In the process of refrigeration which comprises condensing a gaseousfluorinated hydrocarbon refrigerant and then evaporating the same in thevicinity of a body to be cooled, the step which comprises compressingsaid refrigerant in the presence of liquid organic esters selected fromthe class consisting of aromatic diand tri-esters of phosphorus acids,normally liquid long chain aliphatic hydrocarbon monoand di-esters ofphosphorus acids, and normally liquid mixed aliphatic-aromatic esters ofphosphorus acids.

9. In the process of refrigeration which comprises condensing a gaseousfluorinated hydrocarbon refrigerant and then evaporating the same, thestep which comprises compressing said refrigerant in the presence of alubricant conlisting of liquid organic esters of phosphorus acids havingthe following general formula where x, Y and Z represent --H or loweraliphat- 15 ie hydrocarbon radicals but may not all be -H at the sametime. and m, n and o are 1', 2 or 3.

10. In the process of refrigeration which comprises condensing a gaseousfluorinated hydrocarbon refrigerant and then evaporating the 20 same,the step which comprises compressing said refrigerant in the presence ofa lubricant consisting of technical tricresyl phosphate.

11'. The process of refrigeration which comprises compressing a gaseousfluorinated hydrocarbon refrigerant in the presence of a lubricantconsisting of liquid organic esters of phosphorus acids which aresubstantially immiscible in said refrigerant, condensing saidrefrigerant, and then evaporating the same in the vicinity of a body to30 be cooled.

FREDERICK BAXTER DOWNING. ANTHONY F. BENNING.

